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authorAl Viro <viro@zeniv.linux.org.uk>2021-05-17 21:19:35 -0400
committerAl Viro <viro@zeniv.linux.org.uk>2021-05-18 20:06:36 -0400
commit3acca043261fa6268961d152ea2505e217eabcba (patch)
treef8113f1648eb75b189c6cfbf8d638b39299e9ea6
parent3a291c974cf7ffb4fad4df6911b912536e511c9d (diff)
d_path: regularize handling of root dentry in __dentry_path()
All path-forming primitives boil down to sequence of prepend_name() on dentries encountered along the way toward root. Each time we prepend / + dentry name to the buffer. Normally that does exactly what we want, but there's a corner case when we don't call prepend_name() at all (in case of __dentry_path() that happens if we are given root dentry). We obviously want to end up with "/", rather than "", so this corner case needs to be handled. __dentry_path() used to manually put '/' in the end of buffer before doing anything else, to be overwritten by the first call of prepend_name() if one happens and to be left in place if we don't call prepend_name() at all. That required manually checking that we had space in the buffer (prepend_name() and prepend() take care of such checks themselves) and lead to clumsy keeping track of return value. A better approach is to check if the main loop has added anything into the buffer and prepend "/" if it hasn't. A side benefit of using prepend() is that it does the right thing if we'd already run out of buffer, making the overflow-handling logics simpler. Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
-rw-r--r--fs/d_path.c21
1 files changed, 5 insertions, 16 deletions
diff --git a/fs/d_path.c b/fs/d_path.c
index 1a1cf05e7780..b3324ae7cfe2 100644
--- a/fs/d_path.c
+++ b/fs/d_path.c
@@ -329,31 +329,22 @@ char *simple_dname(struct dentry *dentry, char *buffer, int buflen)
static char *__dentry_path(const struct dentry *d, char *p, int buflen)
{
const struct dentry *dentry;
- char *end, *retval;
+ char *end;
int len, seq = 0;
- int error = 0;
-
- if (buflen < 1)
- goto Elong;
rcu_read_lock();
restart:
dentry = d;
end = p;
len = buflen;
- /* Get '/' right */
- retval = end-1;
- *retval = '/';
read_seqbegin_or_lock(&rename_lock, &seq);
while (!IS_ROOT(dentry)) {
const struct dentry *parent = dentry->d_parent;
prefetch(parent);
- error = prepend_name(&end, &len, &dentry->d_name);
- if (error)
+ if (unlikely(prepend_name(&end, &len, &dentry->d_name) < 0))
break;
- retval = end;
dentry = parent;
}
if (!(seq & 1))
@@ -363,11 +354,9 @@ restart:
goto restart;
}
done_seqretry(&rename_lock, seq);
- if (error)
- goto Elong;
- return retval;
-Elong:
- return ERR_PTR(-ENAMETOOLONG);
+ if (len == buflen)
+ prepend(&end, &len, "/", 1);
+ return len >= 0 ? end : ERR_PTR(-ENAMETOOLONG);
}
char *dentry_path_raw(const struct dentry *dentry, char *buf, int buflen)